Emissions from fossil fuel combustion facilities, such as flue gases of coal-fired utilities and municipal solid waste incinerators, typically include mercury. For example, emissions as a result of such operations can include vaporized mercury as elemental mercury, Hg0, and/or mercury-based compounds (e.g., an oxidized form of mercury (Hg+2), such as mercuric chloride or mercuric nitrate).
Many countries regulate emissions of mercury in waste gases because of potential environmental hazards posed by mercury emissions. Facilities that generate gas emissions containing mercury typically utilize a mercury monitoring system to measure total mercury concentration in the emissions to comply with the regulations. As mentioned above, the emissions can include element mercury and/or oxidized mercury.
Certain mercury monitoring systems include a converter that converts the oxidized mercury in a sample emission into elemental mercury, such as by using a mercury converter performing a thermal conversion or cracking process. The mercury monitoring system then measures the total amount or concentration of elemental mercury in the emission using an analyzer, such as an atomic fluorescence spectrometer.
To ensure accurate measurement of the elemental mercury concentration in the emissions, mercury monitoring systems typically include a calibration assembly. The calibration assembly provides vaporized elemental mercury to the analyzer at a particular concentration level to calibrate the mercury monitoring system. After calibration, the mercury monitoring system can be used to measure an amount of mercury present in a gas sample collected from an active smokestack.